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Enzyme Therapy

Other common name(s): digestive enzyme therapy, pancreatic enzyme therapy, systemic enzyme therapy, proteolytic enzyme therapy

Scientific/medical name(s): none


Enzyme therapy involves taking enzyme supplements as an alternative form of cancer treatment. Enzymes are natural proteins that stimulate and accelerate many biological reactions in the body. Digestive enzymes, many of which are made in the pancreas, break down food and help with the absorption of nutrients into the blood. Metabolic enzymes build new cells and repair damaged ones in the blood, tissues, and organs.


Available scientific evidence does not support claims that enzyme supplements are effective in treating cancer.

How is it promoted for use?

Enzymes are sometimes used in mainstream medicine. For example, the approved chemotherapy drug asparaginase is an enzyme. Some enzymes are also used for other serious illnesses. Pancreatic enzymes may be given to treat digestive problems resulting from removal of the pancreas or certain diseases of the pancreas.

However, some alternative medicine practitioners claim that digestive enzyme supplements not only relieve digestive problems, such as ulcers and food allergies, but also strengthen the immune system, improve circulation, ease sore throat pain, aid weight loss, and relieve hay fever, ulcers, and rheumatoid arthritis. Proponents also claim that certain enzymes remove a protective coating from cancer cells, allowing white blood cells to identify and attack them.

What does it involve?

Human cells naturally produce about 10,000 different enzymes which are essential in normal metabolism. Enzyme supplements are extracted from animal organs and some plants such as pineapple and papaya (see Bromelain). Among the most popular enzyme supplements are pancreatic enzymes, which come from an animal pancreas.

Enzyme supplements are available in pills, capsules, and powders. Supplements often consist of combinations of several enzymes. Large amounts of the supplements are often taken each day. There is currently no established safe or effective dosage.

Enzyme therapy is a part of some forms of metabolic therapy, including Gerson therapy and the Kelley and Gonzalez programs. (For more detailed information on these regimens, see our documents on Gerson Therapy and Metabolic Therapy.)

What is the history behind it?

Pancreatic enzymes were reportedly first used to treat cancer in 1902 by John Beard, a Scottish scientist. German researchers later used enzyme therapy to treat patients with multiple sclerosis, cancer, and viral infections. Some enzyme mixtures are still commonly used in several European countries.

Dr. Edward Howell introduced enzyme therapy to the United States in the 1920s. He believed that by eating raw meat, people created an enzyme surplus in the body, which resulted in better health and increased resistance to disease. Other practitioners have advocated the use of enzyme therapy since then, often as part of a larger metabolic therapy regimen. At least one enzyme preparation is currently being studied in the United States for use along with chemotherapy in cancer patients.

What is the evidence?

There have been no well-designed studies showing that enzyme supplements are effective in treating cancer. Experts question whether enzymes taken by mouth can reach tumors through the bloodstream, as the enzymes are broken down into amino acids before being absorbed in the intestine.

Studies of enzyme supplements to ease the side effects of cancer treatment have had mixed results. Two studies done in India reported that side effects of radiation therapy in cancer patients taking pancreatic enzyme supplements were less severe than in those taking a placebo. However, these studies were not blinded, meaning patients and their doctors knew whether they were taking the actual enzymes. This means that the results might have been affected by the expectation of improvement, or placebo effect. A blinded German study in which patients did not know whether they were taking the enzymes or placebo pills did not find any benefit.

Several studies done mainly in Eastern Europe have looked at the possible effects of adding enzyme supplements to mainstream cancer treatment. They have generally found that supplements may improve quality of life and could possibly have other benefits. However, these studies are not considered scientifically strong. They looked back in time at patients who were already treated and were not randomized or blinded. A randomized study of the addition of enzyme therapy to standard chemotherapy for multiple myeloma patients is under way in the United States.

A small study of patients with pancreatic cancer—conducted by Dr. Nicholas Gonzalez and published in Nutrition and Cancer in 1999—found that patients treated with pancreatic enzymes survived longer than typical patients with pancreatic cancer. However, in a recent review of alternative cancer therapies, an expert in integrative oncology research methods noted that, "The study was small and obviously prone to several biases. Not only is the comparison with national averages unadjusted for confounders, but the principal results are based on patient selection; twelve patients who did not comply with treatment were excluded from analysis." Well-designed scientific studies control or adjust for confounders, factors besides the method being studied—such as age or cancer stage—that can affect outcome. They have a control group that receives the standard treatment alone, and they generally also include patients who did not complete treatment in the final analysis.

A randomized clinical trial has been sponsored by the National Cancer Institute to evaluate the Gonzalez regimen for treating pancreatic cancer, but no results of this trial have yet been published in a peer-reviewed medical journal.

Are there any possible problems or complications?

This product is sold as a dietary supplement in the United States. Unlike drugs (which must be tested before being allowed to be sold), the companies that make supplements are not required to prove to the Food and Drug Administration that their supplements are safe or effective, as long as they don't claim the supplements can prevent, treat, or cure any specific disease.
Some such products may not contain the amount of the herb or substance that is written on the label, and some may include other substances (contaminants). Actual amounts per dose may vary between brands or even between different batches of the same brand.
Most such supplements have not been tested to find out if they interact with medicines, foods, or other herbs and supplements. Even though some reports of interactions and harmful effects may be published, full studies of interactions and effects are not often available. Because of these limitations, any information on ill effects and interactions below should be considered incomplete.

There is very little information available on the safety of enzyme supplements. Some manufacturers recommend that people taking blood-thinning medications speak with their doctors before taking enzyme supplements.

Care should be taken to make sure that any diet containing raw meat or juices from raw meat is free from bacterial contamination, especially for people with weak immune systems.

Some people are allergic to the materials from which the enzymes are made. Be sure to know the source of any enzymes you are considering.

Women who are pregnant or breast-feeding should speak with their doctor before using this method. Relying on this type of treatment alone and avoiding or delaying conventional medical care for cancer, may have serious health consequences.

Additional resources

More information from your American Cancer Society

The following information on complementary and alternative therapies may also be helpful to you. These materials may be found on our Web site (www.cancer.org) or ordered from our toll-free number (1-800-ACS-2345).

Dietary Supplements: What Is Safe?

The ACS Operational Statement on Complementary and Alternative Methods of Cancer Management

Complementary and Alternative Methods and Cancer

Placebo Effect

Learning About New Ways to Treat Cancer

Learning About New Ways to Prevent Cancer


Cassileth B. The Alternative Medicine Handbook. New York, NY: W. W. Norton & Co; 1998.

Dale PS, Tamhankar CP, George D, Daftary GV. Co-medication with hydrolytic enzymes in radiation therapy of uterine cervix: evidence of the reduction of acute side effects. Cancer Chemother Pharmacol. 2001 Jul;47 Suppl:S29-34.

Ernst E. Complementary therapies in palliative cancer care. Cancer. 2001 Jun 1;91(11):2181-5.

Gonzalez NJ, Isaacs LL. Evaluation of pancreatic proteolytic enzyme treatment of adenocarcinoma of the pancreas, with nutrition and detoxification support. Nutr Cancer. 1999;33:117-124.

Green S. Nicholas Gonzalez treatment for cancer: Gland extracts, coffee enemas, vitamin megadoses, and diets. Scientific Rev Alt Med. 1998;2(2):25-30. Revised April 2000. Accessed at: www.quackwatch.org/01QuackeryRelatedTopics/Cancer/kg.html on June 11, 2008.

Gujral MS, Patnaik PM, Kaul R, Parikh HK, Conradt C, Tamhankar CP, Daftary GV. Efficacy of hydrolytic enzymes in preventing radiation therapy-induced side effects in patients with head and neck cancers. Cancer Chemother Pharmacol. 2001 Jul;47 Suppl:S23-28.

Martin T, Uhder K, Kurek R, Roeddiger S, Schneider L, Vogt HG, Heyd R, Zamboglou N. Does prophylactic treatment with proteolytic enzymes reduce acute toxicity of adjuvant pelvic irradiation? Results of a double-blind randomized trial. Radiother Oncol. 2002 Oct;65(1):17-22.

Memorial Sloan Kettering Cancer Center. Proteolytic Enzyme Therapy. Accessed at: http://www.mskcc.org/mskcc/html/69342.cfm on June 11, 2008.

Sakalova A, Bock PR, Dedik L, Hanisch J, Schiess W, Gazova S, Chabronova I, Holomanova D, Mistrik M, Hrubisko M. Retrolective cohort study of an additive therapy with an oral enzyme preparation in patients with multiple myeloma. Cancer Chemother Pharmacol. 2001 Jul;47 Suppl:S38-44.

Vickers A. Alternative cancer cures: "unproven" or "disproven"? CA Cancer J Clin. 2004;54(2):110-8.

Note: This information may not cover all possible claims, uses, actions, precautions, side effects or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for consultation with your doctor, who is familiar with your medical situation.

Last Medical Review: 11/01/2008
Last Revised: 11/01/2008